The present invention relates to an ultrasonic wave nebulizer for converting water or solution which includes a chemical substance to mist by applying ultrasonic wave vibration to water or said solution.
Conventionally, some systems for converting water to mist have been known. Some of them are (a) an electrode type system which has a pair of electrodes in water which is subject to atomization to generate joule heat by flowing current between electrodes and evaporating water, (b) a pan system which heats water in a pan, (c) a warm air-flow system which evaporates water which is included in porous material by applying warm air-flow to water, and (d) an ultrasonic wave vibrator type which excites water with ultrasonic wave energy. Among them, an atomizer or a nebulizer except an ultrasonic wave vibrator type has the disadvantage that the atomization efficiency which is defined as the ratio of the generated mist to input power is poor, since 539 cal of vaporation heat is necessary for atomizing 1 cc of water. The ultrasonic wave vibration type has 20 times as high efficiency as that of other types of nebulizers in atomizing efficiency, but has the disadvantage that generated mist is cool, and the operation of the nebulizer decreases the room temperature. This is uncomfortable to a human body in winter. Further, a higher atomizing efficiency for an ultrasonic wave vibration type is desirable.
One disadvantage of a prior ultrasonic wave vibration type nebulizer is that bacteria and/or fungus included in water is dispersed into air. Japanese patent laid open publication 238237/1990 proposed a solution to that disadvantage, by heating water by using a heater installed in a water container.
However, that publication has the disadvantages that the structure of the apparatus is complicated since a vibrator and a heater are mounted separately, and further, a heater is installed in water, and control of a heater is complicated so that a heater operates after water is heated sufficiently for killing bacteria and/or fungus. Thus, a timer circuit or a thermostat circuit must be coupled with a heater. Further, a heater installed in water raises a problem of electrical insulation.